RenderStyle no longer needs to be friends with StyleResolverState

StyleResolverState no longer needs to reach into the private methods
on RenderStyle and thus no longer needs to be declared as a friend.

BUG=237268
R=leviw@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19771020

git-svn-id: svn://svn.chromium.org/blink/trunk@154683 bbb929c8-8fbe-4397-9dbb-9b2b20218538